The present invention relates to systems for keeping account of predetermined homogenous units by means of an article bearing information and an external device for imprinting and/or operating on the information. More particularly, the invention is an improvement to systems of the kind described in a commonly-assigned French patent application Ser. No. 77 09822, entitled SYSTEM FOR KEEPING ACCOUNT OF PREDETERMINED HOMOGENOUS UNITS, which was filed in France on Mar. 31, 1977, and in corresponding U.S. application Ser. No. 889,517.
Systems of this kind include a card-like article which carries an initial quantum or balance and which records amounts corresponding to services or goods received or supplied. There are also a device or machine capable of imprinting the initial balance on the article, a device capable of altering the available balance on the article by an amount corresponding to the required or received services or goods, the supply of which is validated by the imprinting device; and a connection system between the article and the external devices.
The object of such systems is to make it possible to create recording or transaction media capable of recording whole numbers of units. The media may be used to note and to keep a record of the data involved in the transaction or recordal which takes place.
The arrangement which is described in the aforementioned patent application includes in particular an information bearing article, formed by a card for example, on which is recorded, in coded language, a certain balance of services or goods to be supplied, in the form of a certain number of separate and equal units.
When a user obtains a card, the card contains in its memory a predetermined credit which can be drawn upon as the user wishes. Eventually the credit value decreases from its initial value to a value of zero.
To avoid fraud, the memory of the card cannot be re-used once the total credit available has been utilized. The card, once void, cannot be used again and must be surrendered by the user when he wishes to obtain a new card.
If the card is to allow a large number of services or goods to be obtained, the initial value imprinted on it may be very great, which means that the expenditure at the time of purchasing the card is considerable.
It therefore appears desirable, to make the card more economical and easier on the pocket, to provide for the possibility of its being validated in sections.
The present invention makes "replenishment" possible, while at the same time ensuring that the system is still very difficult to use fraudulently.